1. Field of the Invention
The present invention relates to a plastic magnet precursor containing a magnet powder and a thermoplastic resin powder, a production method therefor, and a plastic magnet produced by the method.
2. Description of the Related Art
Conventionally, a plastic magnet is produced by compression molding, extrusion molding, or injection molding using a mixture of a magnet powder and a thermoplastic resin powder, or a compound of a granulated product, in which the granulated product is prepared by crushing or breaking through strand cutting, underwater cutting, hot cutting etc., a kneaded product obtained by kneading the mixture (for example, see JP 09-312207 A).
When using a mixture of the above composition as a plastic magnet precursor which is a raw material for a plastic magnet, a difference in specific gravities of a magnet powder and a thermoplastic resin powder becomes extremely large, and thus the magnet powder and the thermoplastic resin powder are liable to separate due to the difference in their specific gravities. There arises a problem in that it is difficult to continuously supply the magnet powder and the thermoplastic resin powder to a next process step in a state retaining a constant ratio.
Further, when using a compound as a plastic magnet precursor which is a raw material for a plastic magnet, the compound itself is subjected to thermal history and shearing history in a kneading step. Therefore, there arises a problem in that heat deterioration and oxidation of the thermoplastic resin powder and destruction of the magnet powder occur, and acceleration of the oxidation of the thermoplastic resin powder due to the magnet powder is considerable.